Questions tagged [log-amplifier]
Logarithmic amplifier ("Log Amp").
20 questions
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Fine tuning of anti-log op-amp for LED driving
I have a 10-bit DAC that outputs a voltage between 0 and 3V. This signal controls a current-driver for LEDs. I need to compensate the "log" behavior of the LEDs, otherwise the first steps ...
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Simulation of log configuration for op-amp
I'm quite new to pspice and I'm trying to simulate the dc transfer function of an op-amp in log configuration.
Here my circuit. I'm using Kicad and ngspice:
R3 and R4 are there because it gave me ...
- 1,450
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Can I compress the dynamic range of ns pulses to better fit ADC range using log amp or mixer?
I have an experiment in which the signal I want to measure is a 1 ns pulse that occurs somewhere around 0-100 ns after a trigger. I want to digitize the pulses to extract the time they occurred and ...
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Multiplier and divisor using logarithmic and anti-logarithmic op-amps, issue with output
I was tasked to make 4 processes using operational amplifiers: adding, substraction, multiplication, and division.
However, only the add and substract operations work: whenever I try to multiplicate ...
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Simulating voltage divider?
Over the past weeks, I've been looking into an analog method of dividing 2 voltages such that V1/V2=Vout. I found many sources on Google using methods like log and antilog amplifiers or a multiplier, ...
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Op-Amp Based Multiplier LTSpice Simulation
I'm supposed to make a multiplier with log amplifier configuration using LM741 op-amps and 1N4001 diodes. I found this circuit configuration in this Youtube video. However, the output voltages I get ...
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Is this IC damaged or fake?
I am trying to test a AD8307. Here are my connections:
(pins not shown are left unconnected, and also pin 8).
I get a quiescent output voltage at pin 4 of about 850 mV with respect to ground, which, ...
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Why does my diode log amplifier in LTspice not match theory?
I am trying to learn about analog multipliers, and I'm trying to implement one using a log-antilog design. I am currently having some difficulties with the log part because simulating an ideal ...
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Does a wide-band, high-current, inline ammeter circuit already exist?
I have an application where I would like to measure currents up to 1000 A, inline, but am also interested in using the same circuit for a low current part of the cycle. The thought is that if I can ...
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replacing AN6878 led driver IC
I'm trying to replace the obsolete AN6878 led driver (logarithmic response, used for audio level indicator) with a modern and available solution.
I'd like to keep the same functionality of the ...
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Logarithmic amplifier with high slew rate -- mutually exclusive?
Does anyone know if the basic construction of a log amp (with a diode or BJT providing feedback from output to input) is in conflict with any ability to reach high slew rates?
I've been looking (...
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Analog multiplier using logarithmic and anti-logarithmic opamp output problem
I'm trying to build a analog multiplier that takes in two voltages and produces the product of them. I have tried to simulate a circuit. Simulation with this methods is part of the objectives in the ...
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Why are all log amp examples with common base logging transistors?
I am not experienced with log amps, and am trying to learn about them.
Every log amp article has the base of the logging transistor grounded.
simulate this circuit – Schematic created using ...
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Opamp detection of extremely tiny voltage
I am working on a project that requires measuring absorbance of a solution.
The circuit consist of an emitter led, a photodiode attached to an opamp with \$10^7\$ gain (TIA).
The solution absorbs ...
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How to convert exponential output to linear output
I have a sensor which gives me roughly exponential output from 0 to 6 volts. How would I convert this to a linear range?
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Sound pressure to db analog
I'm trying to convert an amplified microphone output (it is from 0-5v, biased at 2.5v) to a linear response that correlates with db SPL.
From my research, the output of the microphone directly ...
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Resistor on pin 3 of a Log Amplifier
I'm trying to understand what's the function or R2 resistor in this transdiode log amp configuration. I suppose I've to match the right value to give in order to minimize the effect of input bias ...
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Log amplifier with vacuum tubes
Is there a way to build a log amplifier using vacuum tubes? I would like to have a VU meter (with the proper log response,) but do not want to use solid state components. The output would be to an IN-...
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How to increase max input current of logarithmic amplifier 10x-100x safely?
Is it possible to increase max allowed current of logarithmic amplifier to say 1A by some workaround without loosing capabilities in lower range: 0..1ma ? For example the TI part LOG112 has few ...
user924
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LM394 is obsolete. What is the new standard log amp circuit?
The traditional logarithmic amplifier circuit is described in National Appnote 311:
This circuit uses the difference of two transistor currents to generate the log of the input over a pretty wide ...
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